adVarChar or adLongVarChar???

I am using the following code to access a stored procedure in my database (from my VB application to my SQL Server database):

Public Function insert_News(ByVal title As Variant, _
                            ByVal author As Variant, _
                            ByVal summary As Variant, _
                            ByVal text As Variant) As ADODB.Recordset
    On Error GoTo ErrorHandler

    Set insert_News = RunSPWithRS_Null("insert_News", _
            Array("@title", adVarChar, 255, title), _
            Array("@author", adVarChar, 200, author), _
            Array("@summary", adLongVarChar, 600, summary), _
            Array("@text", adLongVarChar, 5000, text))
    CtxSetComplete
    Exit Function
   
ErrorHandler:
    On Error Resume Next
    Set insert_News = Nothing
   
End Function

This calls the stored procedure insert_News and passes the 4 parameters. My question is:

For the fields summary and text, should I use adVarChar or adLongVarChar? What is the limit of adVarChar and that of adLongVarChar?

What is the difference between adVarChar and adVarWChar?

Additionally, in another field which I hold currency values in Euros, and the datatype is Numeric (16,2) in the SQL Server. What should I declare the value inside my VB application when I call this stored procedure? Should I use

Array("@amount", adNumeric, 9, amount)

?

Thanks for the time
George
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